150 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Per Cubic 
Centimetre. 
Collected at $ ebb-tide . ane 109 sewage bacteria. 
A » = hour after 4 ebb- tide aa 17 59 - 
” 2) 1 oe) 2¢ 15 0) ” 
. igs bag a before 3 flood-tide 12 is a 
” ” > 9 12 oe) $430) 
ae 4 flood-tide cae as 3 = a 
And on 2nd July, means of two series of analyses. 
Per Cubic 
Centimetre. 
Collected at 1 hour before high water ... 0 sewage bacteria. 
” ” s ” ” ” see 2 Sa ” 
5 s high Waver* ne. 30, eee - 
He » 4 4 hour after high pace cia 0 eee 6 
50 eee pre 53 SA ... Numerous sewage 
bacteria. 
To understand rightly these figures we must remember 
that the numbers of sewage bacteria per cubic centimetre 
of crude domestic sewage are to be reckoned by 
the hundred thousand. Still there are. apparently 
anomalous results in that the water just after high water 
may contain more sewage bacteria than one can regard as 
desirable. This result is, however, easily explained 
away. It is the practice at Aberdovey to liberate the 
sewage from the main outfall during the flood tide so as 
to avoid fouling the sands where bathing goes on. This 
occurs during June and July, in which months my 
samples were collected. When the bathing season is 
over the sewage is, I believe, discharged at all states of 
the tide. Probably, then, the contamination of the 
shore on the site of the tank is much more likely during 
the holiday season than it would be during the mussel 
season in the winter months. It is small, at the worst, 
and it may effectually be prevented by arranging to 
liberate the sewage, during the mussel season, only on the 
ebb-tide. This ought to be as easy to do in the interest 
of the mussel industry in the winter, as the opposite 
procedure is in the interest of holiday-makers in the 
summer. If it is conscientiously carried out, the tank 
will remain unpolluted. 
